Living carbocationic polymerization (LC.sym.Pzn) of olefins (e.g., isobutylene, styrene, various styrene derivatives) coupled with sequential monomer addition has resulted in a variety of new potentially useful materials including narrow molecular weight dispersed homopolymers, macromonomers, blocks, and networks.
One of the challenges in this field, is the synthesis of thermoplastic elastomers, specifically triblocks (or three-armed stars) comprising a soft (rubbery) center block flanked by hard (or glassy) outer blocks. Typically, the soft rubbery block is polyisobutylene and the hard glassy outer block is polystyrene or polyindene or derivatives thereof. In regard to these thermoplastic elastomers, the critical synthesis step is the quantitative and rapid crossover from the first polyisobutylene (PIB.sym.) block to styrene (St) or styrene derivative: EQU PIB.sym.+St .fwdarw.PIB-St.sym.
Because of the similar stability/reactivity of the olefinic monomers involved, these crossovers proceed without much difficulty.
A most desirable feature, which has not heretofore been achieved by LC.sym.Pzn is the one-pot synthesis of amphiphilic diblocks, i.e., A-B blocks in which a hydrophobic block (e.g., PIB) is bonded to a hydrophilic (e.g., poly (methyl vinyl ether) (PMeVE)) block. Such amphiphilic blocks are potentially useful emulsifying or blending agents, detergents, viscosifiers. The synthetic challenge is to develop conditions under which the EQU PIB.sym.+MeVE.fwdarw.PIB-MeVE.sym.
crossover occurs quantitatively and rapidly, and desirable molecular weight PMeVE blocks are attained.